Hematophagous arthropod infestation of animals is a health and economic concern because hematophagous arthropods are known to cause and/or transmit a variety of diseases. Hematophagous arthropods directly cause a variety of diseases, including allergies, and also carry a variety of infectious agents including, but not limited to, endoparasites (e.g., nematodes, cestodes, trematodes and protozoa), bacteria and viruses. In particular, the bites of hematophagous arthropods are a problem for animals maintained as pets because the infestation becomes a source of annoyance not only for the pet but also for the pet owner who may find his or her home generally contaminated with insects. As such, hematophagous arthropods are a problem not only when they are on an animal but also when they are in the general environment of the animal.
Bites from hematophagous arthropods are a particular problem because they not only can lead to disease transmission but also can cause a hypersensitive response in animals which is manifested as disease. For example, bites from fleas can cause an allergic disease called flea allergic (or allergy) dermatitis (FAD). A hypersensitive response in animals typically results in localized tissue inflammation and damage, causing substantial discomfort to the animal.
The medical importance of arthropod infestation has prompted the development of reagents capable of controlling arthropod infestation. Commonly encountered methods to control arthropod infestation are generally focused on use of insecticides. While some of these products are efficacious, most, at best, offer protection of a very limited duration. Furthermore, many of the methods are often not successful in reducing arthropod populations. In particular, insecticides have been used to prevent hematophagous arthropod infestation of animals by adding such insecticides to shampoos, powders, collars, sprays, foggers and liquid bath treatments (i.e., dips). Reduction of hematophagous arthropod infestation on the pet has been unsuccessful for one or more of the following reasons: (1) failure of owner compliance (frequent administration is required); (2) behavioral or physiological intolerance of the pet to the pesticide product or means of administration; and (3) the emergence of hematophagous arthropod populations resistant to the prescribed dose of pesticide. However, hematophagous arthropod populations have been found to become resistant to insecticides.
Prior investigators have described insect carboxylesterase (CE) protein biochemistry, for example, Chen et al., Insect Biochem. Molec. Biol., 24:347-355, 1994; Whyard et al., Biochemical Genetics, 32:924, 1994 and Argentine et al., Insect Biochem. Molec Biol, 25:621-630, 1995. Other investigators have disclosed certain insect CE amino acid sequences, for example, Mouches et al., Proc Natl Acad Sci USA, 87:2574-2578, 1990 and Cooke et al., Proc Natl Acad Sci USA, 86:1426-1430, 1989, and nucleic acid sequence (Vaughn et al., J. Biol. Chem., 270:17044-17049, 1995).
Prior investigators have described certain insect juvenile hormone esterase (JHE) nucleic acid and amino acid sequences: for example, sequence for Heliothis virescens is disclosed by Hanzlik et al., J. Biol. Chem., 264:12419-12425, 1989; Eldridge et al., App Environ Microbiol, 58:1583-1591, 1992; Bonning et al., Insect Biochem. Molec. Biol., 22:453-458, 1992; Bonning et al., Natural and Engineered Pest Management Agents, pp. 368-383, 1994 and Harshman et al., Insect Biochem. Molec. Biol, 24:671-676, 1994; sequence for Manduca sexta is disclosed by Vankatesh et al., J Biol Chem, 265:21727-21732, 1990; sequence for Trichoplusia ni is disclosed by Venkataraman et al., Dev. Genet., 15:391-400, 1994 and Jones et al., Biochem. J., 302:827-835, 1994; and sequence for Lymantria dispar is disclosed by Valaitis, Insect Biochem. Molec. Biol., 22:639-648, 1992.
Identification of an esterase of the present invention is unexpected, however, because even the most similar nucleic acid sequence identified by previous investigators could not be used to identify an esterase of the present invention. In addition, identification of an esterase protein of the present invention is unexpected because a protein fraction from flea prepupal larvae that was obtained by monitoring for serine protease activity surprisingly also contained esterase proteins of the present invention.
In summary, there remains a need to develop a reagent and a method to protect animals or plants from hematophagous arthropod infestation.